Subaru Impreza WRX STi

The engine burbles as we inch out of the carpark and head for the open road. The ride is firm at low speed, the car feeling competition car-taut though surprisingly-supple.

As we leave the outskirts of the township I floor the throttle and the 2.0-litre turbocharged motor answers eagerly, revs rising rapidly as the turbine spins and the car rockets forward.

It's difficult to find a word that describes the Subaru STi's acceleration adequately.

Vivid seems not quite enough. Fierce implies a degree of wildness that is absent, the car's fine chassis and well-sorted all-wheel drive keeping things nicely controllable despite the power and acceleration (the car will hit 100km/h in less than six seconds).

Brutal suggests a coarseness that has no place in any discussion of Subaru's new rally-bred road rocket.

The urge is so great that you find the beeper reminding you that a gearchange is needed arrives much more quickly than you're expecting.

Initially I fumble the gearshifts, especially those low in the six-speed gearbox. I make a hash of the shift from first to second as we blast away from Give Way signs. I try to shift too quickly and the result is an awful jerkiness. Taking things a little more slowly and gently and allowing the engine's mighty torque to do the work is a much better and smoother solution, though my passenger Colin Smith makes a better fist of that technique when he takes the wheel for the second 80 kilometres of our drive on the STi's press introduction. Me, I'm a bit of a rev-head and I'm often probably a gear lower than I need to be.

The STi darts through a roundabout and sprints towards the hills, eating up the undulating straight in a burst of potent acceleration.

I button off for a crest I'd discovered earlier in the morning. The crest has an abrupt lip and I have no desire to fly the Subaru off it, even gently. Winding into the hills the car comes into its own, sprinting vividly from corner to corner, the engine singing and the change gear buzzer pinging. Grip is phenomenal even on roads still damp with the morning dew in sheltered places.

The brakes are solid and reassuringly-strong, the gearshift precise and commendably quick if a little notchy.

The meaty torque means lighting-fast changes aren't really necessary. That torque also means that in many cases you can take corners a gear higher than you might expect.

The torque also means you're seldom embarrassed by being two gears too high when you forget where you are in the six-speed 'box - an easy mistake to make when you're more used to a five-speed.

Cornering grip is staggering and the car is unfazed by mid-corner bumps. The suspension is supple and the car is comfortable for driver and passenger at speed. The excellent seats help here. They are well-padded and provide excellent shoulder and rib support without being intrusive.

They feel as if they've been designed by keen drivers for keen drivers. Steering is precise and the car is enormous fun to drive. Pressed hard into slowish corners there's a touch of understeer, but the changes to the rear suspension geometry improve turn-in over previous models.

The 80 kilometres pass too quickly, and I get a real impression of just how accelerative and g-force inducing the STi is when Smith takes the wheel for the run back to the press launch base.

Hanging on to the steering wheel and operating the gear lever and foot pedals means you're prepared - relatively-speaking anyway - for the accelerative and decelerative forces when you're in the drivers seat.

From the passenger's seat, though, you become aware of the fore and aft and lateral forces this car is capable of. And they're massive.

When we trickle back into the carpark we're both wearing huge grins. The STi has proven to be a real blast. The only regret is that the drive hadn't been longer.

So what is an Impreza STi. Quite simply, it's a modified version of the already potent WRX Impreza.

But the big change is in peak torque. The WRX's 292Nm gives that car excellent acceleration.

The STi's 373Nm (peaking at 4000rpm) produces an effect like a giant hand pushing you back into the form-fitting race-style seats every time the throttle is floored. The massive thrust is more noticeable when you're a passenger, and a brisk run in the country with a good driver wouldn't be a good idea for anyone inclined to car sickness. The driver, of course, will be loving every nano-second of the driving experience and probably won't hear your intimations of car-sickness till you yell very firmly - and loudly - "Stop now!"

STi tweaks include a 15mm taller bonnet scoop to feed more air into the 11 percent larger intercooler which has a water spray system - with a larger reservoir - to keep temperatures down. The turbocharger used is exclusive to the STi.

The engine has active variable valve control and the computer-controlled engine management system has been reworked. The multi-point fuel injection provides better throttle response and more torque at lower and mid-range engine speed.

The cylinder block and liners have been strengthened and special pistons and strengthened conrods are fitted. The valves are hollow-stemmed to help dissipate heat.

The power is fed to the four-wheel drive chassis via a new six-speed short-throw gearbox which has its own oil pump. The gearbox has been strengthened to cope with the high torque, and the car gets a larger clutch plate.

A viscous centre differential feeds the power equally to the front and rear axles. It senses changes in tyre grip and sends more power to then end of the car which has better traction. A rear limited slip differential distributes torque to the rear wheel with most grip.

The MacPherson strut suspension has a wider front track, created by using 225/45 ZR17 tyres on the 17-inch diameter alloy wheels. At 1490mm, front track is 5mm wider than the WRX's. Rear track is the same at 1480mm. The wheelarches are flared on the sedan (the STi is available as a hatchback wagon too).

A titanium tower brace in the engine bay strengthens the front suspension. The front lower arms are forged from aluminium, and the car's suspension has been re-designed to sharpen handling.

At the rear the crossmember has a strengthened attachment to the chassis. The rear diff has been raised to increase roll centre height to improve suspension response in cornering.

The suspension, though stiffer than the WRX's supple set-up, retains long travel for good bump absorption.

The rack and pinion power steering has a quick 15:1 ratio.

Brakes are Italian Brembo units, four-spot callipered at the front and two-pot at the rear. ABS and electronic brake distribution is standard and G-sensors on both sides improve stability under heavy braking. The 17-inch wheels allow bigger diameter brakes than on the 16-inch-wheeled WRX.